Receiver providing masking of an error in a digital signal, and a transmission system including such a receiver

A receiver, comprising:

• receiving means for receiving a first digital signal representing a wide-band digital signal which has been encoded into sub-band signals which are each made up of successive signal blocks having a predetermined number of samples of that sub-band signal, the samples in the signal blocks of the sub-band signals having been quantized to produce quantized sub-band signals in the signal blocks;
• error correction means for correcting errors in and converting the first digital signal into a second digital signal having signal information, which includes the quantized samples in the signal blocks and scale factor information relating to scale factors for the signal blocks, included in successive frames of the second digital signal;
• control signal generating means for generating a control signal if an error exists in the signal information which could not be corrected by said error correction means, said control signal generating means being adapted to generate the control signal if an uncorrected error exists in a scale factor for a signal block of the signal information;
• error masking means for replacing the scale factor having the uncorrected error with an extrapolated value from one or more scale factors belonging to one or more preceding signal blocks of the same sub-band signal as the signal block which has the scale factor having the uncorrected error if the control signal is generated;
• derivation means for deriving the quantized samples in the signal blocks and the scale factor information relating thereto from the signal information, and producing replicated samples in the signal blocks which substantially correspond to the samples in the signal blocks of the sub-band signals;
• and
• synthesis filter means for constructing a replica of the wide-band digital signal in response to the replicated samples in the signal blocks.

A digital transmission system, comprising:

• a transmitter having
• first encoding means for receiving a wide-band digital signal, said first encoding means including (i) sub-band coding means for generating a plurality of sub-band signals from the wide-band digital signal, each of the sub-band signals being made up of consecutive signal blocks which each contain a predetermined number of samples of that sub-band signal;
• (ii) quantization means for quantizing the samples in the signal blocks of the sub-band signals to produce quantized samples in the signal blocks;
• (iii) bit allocation means for generating bit allocation information denoting how many bits the samples in each of the signal blocks are to be quantized by;
• and (iv) scale factor information generating means for generating scale factor information relating to scale factors for the signal blocks;
• combining means for combining the quantized samples in the signal blocks and (b) (i) the bit allocation information and (ii) the scale factor information relating thereto in successive frames of a second digital signal;
• second encoding means for converting the second digital signal into a third digital signal which is error correction encoded;
• and
• application means for applying the third digital signal to a transmission medium;
• and
• a receiver having
• receiving means for receiving a replicated third digital signal from said transmission medium which substantially corresponds to the third digital signal applied to the transmission medium;
• error correction means for correcting errors in and converting the replicated third digital signal into a replicated second digital signal which substantially corresponds to the second digital signal, the replicated second digital signal having signal information, which includes (a) the quantized samples in the signal blocks and (b) (i) the bit allocation information and (ii) the scale factor information relating thereto, included in successive frames of the replicated second digital signal;
• control signal generating means for generating a control signal if an error exists in the signal information which could not be corrected by said error correction means, said control signal generating means being adapted to generate a first, control signal if an uncorrected error exists in a quantized sample in the signal information;
• derivation means for deriving (a) the quantized samples in the signal blocks and (b) (i) the bit allocation information and (ii) the scale factor information relating thereto from the signal information, and producing replicated samples in the signal blocks which substantially correspond to the samples in the signal blocks of the sub-band signals;
• error masking means for either (a) replacing the quantized sample having the uncorrected error with a quantized sample having a zero amplitude or (a) causing a replicated sample having a zero amplitude to be produced as a result of the quantized sample having the uncorrected error;
• and
• synthesis filter means for constructing a replica of the wide-band digital signal in response to the replicated samples in the signal blocks.